Horn mouth termination

[mah]

Re 3M removable double sided tape. The Office Product comes on a dispenser/reel under the Scotch brand. Same family of product but not limited to the short strip lengths.

[Steve Mac]

Yeah, but so will those big horns behind!!

Learn by doing - it's a time tested method.....

Right...
Actually I'm not that worried because they bolt together...and can be walked through the smallest of doorways...

[Steve Mac]

...As to the flush edge joint, I make the foam fit the horn rather than vice versa. You could overhang the foam a bit, then trim it flush, using the horn to guide the knife. BTW, your knife isn't sharp enough yet, I can tell by the pics. Seriously, if you can't shave your arm with it, it's too dull. The length of a fillet knife lets you slice. A short blade, while sharp, will catch and tear.

When you get close, mitre the ends and go all the way around (like a picture frame). And get a boot on that driver. Or...do watcha want.

Great post...thanks!
But I'm still shaking my head on this one...stubborn goat I am.
But I took a step to "hear" the foam roughed in to see what it would sound like:

I've been listening all night and its made a big difference.
It is much more pleasant to listen to at higher volumes.
I'm trying to hear an Altec horn and it seems like it's gone.
Anyway, this idea is a helluva upgrade. The sound feels easier and my ears
are much less fatigued after this session. Simply WOW! (said like Jack Kerouac).

[Steve Mac]

Right on! At worst it should be at least expansion neutral just like when folding a horn, as any constriction will create reflections back to the throat.

GM

I suppose you know that I've learned this the hard way.

[Steve Mac]

That looks right to me. You are continuing the horn profile almost 360 degress, which is what Jean-Michel Le Cl?ac'h does with his horn profiles.
Also you are using a soft termination, that should be good.
And the termination now does not intrude into the mouth.

Well worth a try, I would say!

I'm going to have to look at this gentleman's work.
I thought I found his site at one time and looked and wondered...
Anyway, do you have an opinion on the differences/benefits/problems
with the soft termination as opposed to a hard termination?

[Steve Mac]

Based on Peavey's and Dr. Geddes's work, my SWAG is that the foam's absorption factor has a bigger impact than its curvature. For sure, the solid flares I experimented with didn't reach a point of diminishing returns until it radius was ~1/3 WL of its LF cut-off and rolled over some odd number of degrees (~ 237 IIRC). I assume JMMLC's more recent theoretically mathmatically correct termination is at least as good and may measure better, though I'd be surprised if there's an audible difference. What makes his better overall though is that his way results in a smaller mouth o.d..

GM

As usual there are some interesting ideas buried in yer posts.
As to the soft termination...is the benefit that it simply buries in a direct,
non-flare-perfected manner, the reflections at the lip of the mouth?
...possible that it's at the expense of some horn efficiency too?

wrt: until it radius was ~1/3 WL of its LF cut-off
I get ~12*(1100/(500*3)) out of that statement which is a radius over 8 inches?!!!
...again the jmmlc guy...

[Panomaniac]

Well I'm no expert - but I've seen this idea around for 20 odd years.
Jean-Michel and I came from the same starting point, an admiration for the horn work of Mr. Iwata.

Iwata was an engineer working to lessen the shock waves at the mouths of high speed train tunnels in Japan. He looked at gun silencers, IIRC. He ended up with a series of slots at the mouth - slots that get progressively farther apart. The idea is to kill the shockwave by making the impedance of the tunnel progressively lower. The progessive slots do this.

So Mr. Iwata adapted this system to his horns with great sucess. See photo of an Iwata bass horn below.

Jean-Michel started there and discoverd that curling the lip all the way around toward the back also eleminated diffraction at the mouth. No soft termination needed. I do not know if there is actually a "shockwave" at the horn mouth, but for sure there is diffraction. The rubber lips help kill this. The transistion of the sound wave from hard horn to soft air is made less aburpt. That's a good thing.

There you have it! So I think your idea with the fibergalss curl is right on target.

[Steve Mac]

.... So I think your idea with the fibergalss curl is right on target.

fiberglas! NO!
Thank you for this information...this is all very interesting to me!